The present invention relates to digital audio signal reproducing apparatus for successively reproducing audio signals of a plurality of tracks.
The digital audio amplifier has been in practical use which receives a digital audio signal directly as they are, processes the received digital audio signal via a DSP (Digital Signal Processor), converts the thus-processed signal into analog representation and then amplifies and outputs the analog signal. Because such a digital audio amplifier is digitally connected to a digital audio signal reproducing apparatus, it can reliably prevent a possibility of undesired signal deterioration such as introduction of noise into the signal. In addition, there is no need to repeat A/D and DA conversion operations when signal processing is carried out within the amplifier via digital circuitry such as DSP circuitry, and thus the digital audio amplifier can also advantageously avoid signal deterioration that would result from the repeated A/D and DA conversion operations.
Digital audio signals are recorded on a plurality of tracks with characteristics corresponding to their respective sources, which means that all the audio signals are not recorded with same recording characteristics. For example, such recording characteristics relate to an ON/OFF setting of emphasis, sampling rate, etc. of the audio signal.
With the traditional analog amplifier, it is not necessary at all to take into account the above-mentioned characteristics of digital recording because analog signals having been converted in advance from digital form are input to the amplifier. However, with the digital audio amplifier, where digital audio signals recorded with various recording characteristics are input directly as they are, there arises a need to process the input signals using processing settings that correspond to the recording characteristics of the signals. Thus, when a variation in any one of the recording characteristics occurs between successive input digital audio signals, i.e. when a newly-reproduced track has a different recording characteristic from a last-reproduced track, the settings of the processing circuitry, such as DSP circuitry, must be changed accordingly, which would take a time in the order of 200-500 msec.
Thus, the ordinary-type digital audio amplifier is arranged in such a manner that, when some variation in any of the recording characteristics occurs between successive input digital audio signals, it mutes the output audio signals during the time necessary for changing the settings of the processing circuitry (200-500 msec.) and thereby prevents noise, produced due to the setting-changing operations, from being audibly output through a speaker.
However, because a digital audio signal reproducing apparatus, which is a digital audio signal supply source, is connected with the digital audio amplifier only via a digital audio line such as an optical fiber or coaxial cable, the reproducing apparatus can not identify states of the digital audio amplifier. Thus, even when the digital audio signal reproducing apparatus is muting the output, it keeps reproducing and delivering a digital audio signal to the digital audio amplifier. As a consequence, when tracks of different settings are reproduced, they tend to lack signals of their leading or head portions.
Although it is generally rare that a single audio CD mixedly includes tracks of different recording characteristics, such mixed inclusion of tracks of different recording characteristics may often present the above-discussed inconvenience in cases where a plurality of tracks extracted from a plurality of sources are combined into a single audio CD.